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S.U. .E.R.M.A.N. SU nyaev-Zeldovich B - P olarization E xplo R ing M icrowave AN tenna. - PowerPoint PPT PresentationTRANSCRIPT
S.U. .E.R.M.A.N.
SUnyaev-Zeldovich B-Polarization ExploRing Microwave ANtenna
Laila Alabidi (UK); Paul Beck (Austria); Marcos Cruz
(Spain);Árdís Elíasdóttir (Denmark); Henning Gast (Germany);
Lara Sousa (Portugal); Thomas Kronberger (Germany);
Gemma Luzzi (Italy); Jens Melinder (Sweden); Peter Predehl
(Germany); Oliver Preuß (Germany); Mirko Tröller (Finland);
Elisabetta Valiante (Germany); Paul Anthony Ward (Ireland)
OVERVIEW
•Short Introduction to the Mission;
•Science case:
−B-Modes;
−Sunyaev-Zel‘dovich;
•Engineering:
−Mission scenario;
−Spacecraft design/Platform;
−Telescope and Instrumentation;
•Cost and administrative affairs;
•Summary
INTRODUCTION
The Su erman Mission
As the name suggests, this mission will be leaping over tall orders to achieve what might appear to the mere mortal as impossible!
•The most accurate and complete measurement of the B-mode polarisation anistropy to date;
•An all sky Sunyaev-Zel‘dovich survey, at a resolution of 1 arcmin;
IMPORTANCE FOR DARK MATTER AND DARK ENERGY
•It is an indication for a variable cosmological constant (Quintessence);
•It is a measurement of the reionization bump which is due to dark matter annihilation and will therefore probe primordial dark matter;
IMPLICATIONS OF DARK ENERGY (I)
IMPORTANCE OF DARK MATTER (II)
B-MODE POLARIZATION
B-MODE SCIENCE
•Polarization of CMB is due to Thomson scattering which occurs post photon decoupling and is enhanced during reionization;
•The amount of polarization depends on the free electron density in the direction of observation;
•Gravitational waves lead to an in-homogeneity in electron density in the plane perpendicular to the direction;
•This in-homogeneity leads to a phase shift in the photons, leading to B-mode polarization with an amplitude
21cos2 yxEEU
BY MEASURING THE B-MODE WE CAN (I):
•Independantly measure the thickness of the optical depth as measured by WMAP. This is a strong indicator of Dark Matter in the early universe;
•Make an Indirect measurement of gravitational waves;
•Constrain (or obtain a value) on the tensor to scalar ratio (r);
BY MEASURING THE B-MODE WE CAN (II):
•Obtain more information on the type and energy scale of inflationary scenarios;
•Probe quantum gravity;
•Confirm or Refute magnetic Parity Conservation;
•Study Physics of energy scales inaccessible to particle acelerators;
•Probe re-ionization history;
WHY SPACE?
•Stable environment that allows the reduction of system noises
•No disturbances caused by earth´s atmosphere and the earth itself;
INCREASE SENSITIVIT
Y
•All sky coverage that allows:
-Improved statistics;
-Detection of the lowest polarization modes, i. e., PROBE RE-IONIZATION BUMP,
FOREGROUND EMISSION
•Free-free emission (negligably polarized);
•Synchroton emission → low frequencies;
•Dust emission → high frequencies;
•Extragalactic emission from radiogalaxies and weak-lensing;
Deduced by making measurements at
low and high frequency channels
COMPLEMENTARITY AND COMPETITION
•Current missions don‘t have enough sensitivity;
•There are, at least, 8 missions planned for measuring the B-mode:
−Ground-based missions;
−Balloon-borne missions;
−Space missions;
Detectability of B-mode constrained by limited observed
area and atmospheric disturbances
•Our expected sensitivity of r~0,001 is of the same order as that of the next generation ground-based and balloon experiments;
•We will be probing the lower l modes which cannot be done without performing an all sky survey;
SUNYAEV-ZEL‘DOVICH EFFECT
COSMOLOGY WITH THE SUNYAEV-ZEL´DOVICH EFFECT
• Very powerful and versatile tool to study large scale structure of the universe
• Inverse-Compton scattering of the CMB photons off the high energy electrons of the ICM
PHYSICAL PRINCIPLES
• Expressed as a temperature change at dimensionless frequency :
radx
x
rad yTe
exT
41
1CMBbTk
hx
dncm
kTy eT
e
e 0 2
Compton y-parameter:
Kinetic SZE:
c
v
T
T pec
CMB
SZE
BASIC FEATURES
• Mass threshold nearly redshift independent;
• Highly complementary to other observational diagnostics;
Carlstrom et al., 2002
SCIENTIFIC RATIONALE
• Cluster based Hubble diagram: • Uses different electron density dependencies of the SZE
and X-ray emission,
cex
eHA TS
TD
1)(
200
02
0
Quantities evaluated along the line of sight through the centre;
Carlstrom et al., 2002
SCIENTIFIC RATIONALE
• SZ-selected samples almost mass limited;
• Cluster counts and distribution strongly depends on cosmological parameters and cluster formation physics;
Da Silva et al., 2000
• FURTHER POSSIBLE
APPLICATIONS:
– Intra-supercluster gas;
– Time dependence of dark
energy density (Bartelmann
et al. 2005);
– Test TCMB ≈ (1 + z) by ratio of
SZ at 2 different frequencies;
– Kinetic SZE unique way to
measure large scale velocity
fields;Couchman, 1997
SCIENTIFIC RATIONALE
NECESSITY OF GOING TO SPACE
• The most powerful use of SZE are deep, large scale
surveys;
• Ground based observations suffer from systematics coming
from atmospheric variations;
COMPLEMENTARITY AND COMPETITION
• PLANCK will measure the
SZE but due to relatively
large beam width, resolve
only around 20.000
clusters;
• Atacama Cosmology
Telescope: ground based; OVRO millimetre wavelength array
FOREGROUND AND SYSTEMATICS
• Galactic emission, such as synchrotron and dust
emission and fluctuations of CMB itself;
• Point sources;
• Assumption as spherical symmetry, isothermality and
absence of clumping often used;
EXPECTED RESULTS
• In a ΛCDM we expect
around 20 clusters per
deg2, thus with the all sky
survey we should get
700.000 clusters;
•In a τCDM we expect
around 3 clusters per
deg2, thus with the all sky
survey we should get
105.000 clusters;
ENGINEERING
STARTING WITH PLANCK
Mission Scenario
L2
L2 (after ¼ year)
0,2 rpm
Spacecraft Designstarting from the bottom
380
0
Solar PanelLaunch Adapter (10,5m2)
SPACECRAFT DESIGNstarting from the bottom
356
6
S/C Bus"Service Module", SVM
DOES IT FIT INTO ST-FAIRING?
SolarpanelService Module
V-Grooves
Sec. Reflector
Prim. Reflector
654
5
Shield / Baffle
“TULIP“
V-GroovePanels
S/C Design
Service Module
V-Grooves
PayloadSupport Structure
Telescope
"Tulip"-Extension
THE TELESCOPE
Goals:
SZ Effect• high angular resolution
B-Mode• large field of view • no cross and instrumental-
polarization
Solutions:
• 3m diameter paraboloid aperture stop
• off-axis Gregorian satisfying the Mizuguchi-Dragone condition
INSTRUMENTATION
The focal plane unit – basic layout
• The focal plane size given by the optical design is 5° (or 300 mm in physical units).
• The FPU accomodates two different instruments sharing the same cryostat, the Total intensity Instrument (TI) and the Polarimetry Instrument (PI).
focal plane
TI
PI
To secondary mirror
INSTRUMENTATION
• Filters/Channels- The TI will observe the CMB in 3 channels; 143, 220 and 330 GHz optimized to study the SZ effect.
- The PI will observe in 3 channels; 40, 100 and 220 GHz
• Polarimetry- Uses a combination of a rotating half-wave plate (HWP) and a fixed polarizing grid (FPG) to modulate the signal.
- This technique provides immunity to a number of systematic effect (no detector differencing needed).
INSTRUMENTATION
Filter
PI
TI
INSTRUMENTATION
• Detector array setup
- For each of the six channels there will be an array of hornfed TES bolometers. The arrays will be constructed to fill the focal plane (diameter of 300 mm).
- In total a number of 690 detectors can be fitted inside the focal plane divided between the different channels and instruments (PI/TI).
- The number of detectors is limited by the fact that each horn has to have a diameter of at least the wavelength observed.
INSTRUMENTATION
• Transition edge sensors (TES)
- Has a great advantage in that they can be produced in large arrays (thin film deposition and optical lithography)
- Readout multiplexing technologies (SQUIDs) have been developed/are in development. These makes it possible to readout many detectors at once.
- Have low impedance => more insensitive to vibration.
- Optimal sensitivity is achieved at very low temperatures (100 mK), good cryostat needed. Detector noise power is on the order of 2·10-17 W/√Hz.
INSTRUMENTATION
INSTRUMENTATION
• Sensitivity calculations- In modern bolometers the sensitivity is no longer determined by the detector noise but rather by background optical loading (photon noise) => Larger amount of detectors
- The photon noise in the instrument is complicated to determine (depends, among other things, on transmissivity of the optics and the crystat effectivity).
- In the sensitivity estimates presented here, we are assuming the photon noise level reached by PLANCK.
INSTRUMENTATION
Frequency (GHz) Beamsize*(arcmin)
Time/Beam **(s/beam)
Sensitivity/Beam**(μK/beam)
No. of detectors
40 (PI) 8.6 5.82 3.31 9
100 (PI) 3.4 2.30 2.64 36
143 (TI) 2.6 1.76 3.47 32
220 (PI) 1.6 1.07 3.14 144
220 (TI) 1.6 1.07 2.81 180
330 (TI) 1.0 0.67 9.22 289
INSTRUMENTATION
Telescope Frequency(GHz)
Noise/Beam (μK) Beam FWHM(‘)
Sky Coverage(sq. Deg.)
QUIET 40 0.43 23 4 × 400
PolarBeaR 90150
1.62.4
6.74.0
500
Planck 100143
10.96.0
9.27.1
51840
INSTRUMENTATION
Telescope Frequency(GHz)
Noise/Beam (μK) Beam FWHM(‘)
Sky Coverage(sq. Deg.)
QUIET 40 0.43 23 4 × 400
PolarBeaR 90150
1.62.4
6.74.0
500
Planck 100143
10.96.0
9.27.1
51840
Superman 100 2.30 3.4 51840
The cooling chain includes a hydrogen sorption cooler, providing a 18K stage; a closed-loop Joule-Thomson refrigerator which provides a temperature of 4K; and a diluition refrigerator which provides the final operating temperature of the bolometers of 0.1K, with a cooling power of 100nW.
(Pla
nck H
FI coolin
g sy
stem
)
COOLING SYSTEM
V-Groove Radiator (TO 60k)
20K H2 sportion cooler (TPL)
4K stirling cooler (RAL/MMS)
O,1K 3He/4He dilution Cooler
POWER SUPPLY
• Total Power Requirements: 800W;• Power generation: circular solar array (10,5 sqm);• Distribution and storage:
– Power Control Subsystems– Power Control and distribution unit– Li-Ion Battery → provides electric power during eclipses
AMCS
DATA PROCESSING & TRANSFER
Detector Signal Proc.Unit, SPU
Digital Proc.Unit, DGU
reading outraw dataexpected: 86 kbits/sec
Reducing glitchesand zero-counts
Comp. Entities, storage until TM, backup,
expected: 7430 Mbits/day
TELEMETRY AND TELECOMMAND
For cost reasons only one ground station,+ 1 backup max: 8 hours for transmission, down to 3 hours, depending on antenna
Telemetry rate: 1,5 Mbit/sec, MGA oriented to Earth 1,5 hours/day for transmission timebackup for 2 transmission
Telecommand rate 5kbit/sec, LGA for comunicating with probe independend on attitude
New Norcia ground station
Planck Satellite
satellite
Groundstation
ESTIMATED MASS
• Since we are going to L2 and we are using the Soyuz-Fregat launcher, the maximum mass allowed is:
2200Kg
COST AND ADMINISTRATIVE AFFAIRS
GROUND SEGMENT
• Operation Ground Segment (OGS):– Observation/scanning plan within the spacecraft systems;– Perform the classical spacecraft operations;– Maintenance tasks;
• Science Ground Segment (SGS):– Science Telemetry;– Revelant ancilliary spaceccraft data from OGS;– Transforming data from spacecraft into a scientist handy form;– Distribute this data to scientists;– Realize the data archive and improvement on reduction
algorithmic;
GROUND SEGMENT
ESTIMATED COST
SUMMARY
SUMMARY
• The mission plans to measure B-Polarization of the CMB and
Sunyaev-Zel’dovich effect;
• To do this we must increase the sensitivity and the angular
resolution of previous telescopes;
• Our instrument reaches both of these science
requirements;
• The technical design meets requirements on weight, size,
data rate, etc. ;
• The cost budget is adequate for such a mission;